Does an Increase in Membrane Unsaturated Fatty Acids Account for Tween 80 Stimulation of Glucosyltransferase Secretion by Streptococcus salivarius?

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Abstract
When S. salivarius was grown in batch culture in the presence of various Tween detergents, the fatty acid moiety of the detergent was incorporated into the lipids of its membrane. Tween 80 (containing primarily oleic acid) markedly stimulated the production of extracellular glucosyltransferase and also increased the degree of unsaturation of the membrane lipid fatty acids. The possibility that an increase in membrane unsaturated fatty acids promoted extracellular glucosyltransferase production was examined by growing cells at different temperatures in the presence or absence of Tween 80. The membrane lipids of cells grown at 30.degree., 37.degree. and 40.degree. C without Tween 80 exhibited unsaturated/saturated fatty acid ratios of 2.06, 1.01 and 0.87, respectively. A significant increase in the production of extracellular glucosyltransferse was observed at 30.degree. C compared to cells grown at 40.degree. C. Cells produced more exoenzyme at all temperatures when grown with Tween 80. Thus, an increase in the unsaturated fatty acid content of the membrane lipids was not by itself sufficient to account for the stimulation of extracellular glucosyltransferase production by Tween 80, but the surfactant also had to be present.